The POU Factor Ventral Veins Lacking/Drifter Directs the Timing of Metamorphosis through Ecdysteroid and Juvenile Hormone Signaling

Although endocrine changes are known to modulate the timing of major developmental transitions, the genetic mechanisms underlying these changes remain poorly understood. In insects, two developmental hormones, juvenile hormone (JH) and ecdysteroids, are coordinated with each other to induce developmental changes associated with metamorphosis. However, the regulation underlying the coordination of JH and ecdysteroid synthesis remains elusive. Here, we examined the function of a homolog of the vertebrate POU domain protein, Ventral veins lacking (Vvl)/Drifter, in regulating both of these hormonal pathways in the red flour beetle, Tribolium castaneum (Tenebrionidae). RNA interference-mediated silencing of vvl expression led to both precocious metamorphosis and inhibition of molting in the larva. Ectopic application of a JH analog on vvl knockdown larvae delayed the onset of metamorphosis and led to a prolonged larval stage, indicating that Vvl acts upstream of JH signaling. Accordingly, vvl knockdown also reduced the expression of a JH biosynthesis gene, JH acid methyltransferase 3 (jhamt3). In addition, ecdysone titer and the expression of the ecdysone response gene, hormone receptor 3 (HR3), were reduced in vvl knockdown larvae. The expression of the ecdysone biosynthesis gene phantom (phm) and spook (spo) were reduced in vvl knockdown larvae in the anterior and posterior halves, respectively, indicating that Vvl might influence ecdysone biosynthesis in both the prothoracic gland and additional endocrine sources. Injection of 20-hydroxyecdysone (20E) into vvl knockdown larvae could restore the expression of HR3 although molting was never restored. These findings suggest that Vvl coordinates both JH and ecdysteroid biosynthesis as well as molting behavior to influence molting and the timing of metamorphosis. Thus, in both vertebrates and insects, POU factors modulate the production of major neuroendocrine regulators during sexual maturation.     

Detection of the intercellular adhesion loci (ica) in clinicalStaphylococcus aureus strains responsible for hospital acquired auricular infection

In clinicalStaphylococcus aureus strains, the presence of theica genes, biofilm formation and susceptibility to antibiotics are considered important factors of virulence. In this study, 35 strains ofS. aureus, isolated from auricular infection, were investigated for slime production using Congo red agar (CRA) method, antibiotic susceptibility, presence ofmecA gene, and presence oficaA andicaD gene. The results show that 60% of strains weremecA positive when tested by PCR although 25.7% of strains were oxacillin resistant when tested with ATB STAPH. Qualitative slime production ofS. aureus using CRA revealed that 74.3% ofS. aureus were slime producers. All the strains carried theica gene.     

Polymorphisms of glutathione-S-transferase M1 and T1 and prostate cancer risk in a Tunisian population

Several genes involved in the metabolism of carcinogenesis have been found to be polymorphic in the human population, and specific alleles are associated with increase risk of cancer of various sites. This study is focused on the polymorphic enzymes glutathione-S-transferase M1 (GSTM1) and T1 (GSTT1) that involved in the detoxification of many xenobiotics involved in the etiology of prostate cancer. Objective. To evaluate whether GSTM1 and/or GSTT1 contribute to prostate cancer (CaP) etiology, we studied 110 incident CaP cases and 122 controls. Results. The probability of having CaP was increased in men who had homozygous deleted (non-functional) genotypes at GSTT1 (OR = 2.17; 95% CI = 1–3.79) but not GSTM1 (OR = 0.89; 95% CI = 0.66–1.88). Hence, individuals lacking the GSTT1 gene are at approximately twofold higher risk of developing prostate cancer in comparison with individuals with at least one active allele in the GSTT1 locus. Conclusion. These results suggest that GSTT1 is associated with CaP risk. The effect of smoking associated with the GSTT10/0 genotype was not found to affect the risk of prostate cancer.     

Interactions of Acacia raddiana with herbaceous vegetation change with intensity of abiotic stress

Theoretical models predict that the relative importance of facilitation and competition may vary inversely across gradients of abiotic stress. However, these predictions have not been thoroughly tested in the field, especially in arid and semi-arid environments. In this study, we evaluated how the net effect of Acacia tortilis subsp. raddiana (syn. A. raddiana) trees on the herbaceous species varies across a gradient of water stress in arid Tunisian ecosystems. Our results show that the influence of trees on the herbaceous stratum is beneficial. An Acacia tree improves the richness of herbaceous species around it by two to three times. The positive effect of Acacia raddiana on species composition is characterised in particular by a better development of some species of high pastoral value such as Cenchrusciliaris, Cynodon dactylon, Eragrostis papposa, Sisymbrium irio and Chenopodium album. We fitted the relationship between seasonal rainfall and the relative neighbour effect index, which varied across this gradient, to a linear model. Our results show that herbaceous plant cover, plant biomass, plant density and diversity are higher under a tree canopy and this positive interaction still increase with higher abiotic stress conditions.     

Changes in soil properties and vegetation following livestock grazing exclusion in degraded arid environments of South Tunisia

In this study, characteristics of vegetation and soil properties under continued grazing and exclusion of livestock for 6 and 12 years were examined in a degraded Stipa tenacissima steppe in South Tunisia.     

A Regional Assessment of Changes in Plant–Plant Interactions Along Topography Gradients in Tunisian Sebkhas

Ecosystems - Facilitation among plants in dry ecosystems is crucial for diversity and ecosystem functioning and stability. However, the importance of facilitation in extremely stressful conditions...     

Restoring degraded arid Mediterranean areas with exotic tree species: Influence of an age sequence of Acacia salicina on soil and vegetation dynamics

Acacia salicina Lindl. is an Australian leguminous tree widely planted outside its original distribution as a multi-purpose species, and successfully establishes on degraded areas. The objective of this study was to determine how an age sequence of 3, 5, 9 and 13-year-old A. salicina plantations affected soil properties and flora diversity of an arid Mediterranean steppe. Soil samples were taken from the upper 10 cm of soil under tree canopies and in the associated open spaces. The results showed that tree establishment and development enhanced soil contents of total C, total N, available P and exchangeable K⁺, Ca²⁺, Mg²⁺ and Na⁺. These trends increased significantly with increasing plantation age. At the same time A. salicina facilitated the colonization and development of understory vegetation. Indeed, the number of plant species, the total plant cover, the perennial species density, the plant biomass and the diversity all attained higher values under tree canopies and increased with increasing plantation age. The soil dynamic under 13-year-old A. salicina plantations reflected two phases in the restoration sequence, characterized by nominal changes during tree establishment (0–5 years) and showing marked and rapid changes associated with the start of canopy closure (5–13 years). A. salicina establishment could be an effective and applicable measure to restore soil and vegetation and control desertification in the Mediterranean arid steppes.     

Biodegradation of triphenylmethane dye Malachite Green by <Emphasis Type="Italic">Sphingomonas paucimobilis</Emphasis>

Triphenylmethane dyes belong to the most important group of synthetic colorants and are used extensively in the textile industries for dying cotton, wool, silk, nylon, etc. They are generally considered as the xenobiotic compounds, which are very recalcitrant to biodegradation. Sphingomonas paucimobilis, was isolated from the soil sample collected from contaminated sites of textile industry located in KsarHellal, Tunisia, and it was able to decolorize Malachite Green (MG) dye (50 mg/l) within 4 h under shaking condition (pH 9 and temperature 25°C). The effect of inoculum size, dye concentration, temperature and initial pH of the solution were studied. The results obtained from the batch experiments revealed the ability of the tested bacteria to remove dye. UV–Vis spectroscopy and FTIR analysis of samples before and after decolorization confirmed the ability of the tested strain to decolorize MG. In addition, the phytotoxicity study revealed the degradation of MG into non-toxic product by S. paucimobilis.     

Environmental factors that limit <Emphasis Type="Italic">Stipa tenacissima</Emphasis> L. germination and establishment in Mediterranean arid ecosystems in a climate variability context

In a climate variability context, knowledge about Alpha grass (Stipa tenacissima) seed germination and seedling establishment requirements is a key factor given the relevance of this species in wide areas of North Africa and southern Europe. Such knowledge can help to collect information about current S. tenacissima populations allowing the conservation and restoration in these ecosystems. According to this objective, we conducted a series of laboratory studies to investigate the effects of several ecological factors as temperature, light, salinity, burial depth and drought, in relation to germination capacity and development of new seedlings. The main results revealed that germination was delayed with increasing drought conditions generated by osmotic solutions. Seeds germinated at all the concentrations of NaCl solutions, but germination was completely inhibited at a PEG 6000 solution of ?1.6 MPa. Further, an osmotic potential of ?0.8 MPa inhibited root and shoot growth. Variations in temperature also promoted variable germination rates (GR50). The base germination temperature (Tb (50)) was less than 2 °C for the different osmotic potentials. Burial depth was another limiting factor required for establishment. Despite significant seed production, this study has identified several key limiting points affecting seed germination and seedling establishment which can affect the viability of their populations in the near future.